Power-based systems are designed to address changes in current requirements at the load. A microprocessor load, for example, may change its current consumption by 50 amps or more in a fraction of a nanosecond, or a single cycle. This current spike, or change in current consumption (di/dt) causes voltage variations or spikes, known as droops, on the power supply. A droop is defined as an output voltage change as a function of time, and may include both under-voltage and over-voltage conditions.
These droops are designated as 0th order, 1st order, 2nd order, and so on, according to their duration. A 0th order voltage droop, or 0th droop, manifests itself as a high-frequency noise on the power grid of the load. The 0th droop is the first droop to manifest in a voltage spike event (as compared to the 1st droop, 2nd droop, etc.), and has a very short duration.
The duration of the 0th droop is so short, in fact, that the 0th droop is undetectable using known technology. The 0th droop has not yet been successfully quantified due to its very high frequency (10 GHz and above) compared to the 1st droop (below 1 GHz). Further, for microprocessors, the available technology has been unable to accurately measure the 0th droop from outside the chip. The droop component is expected to be local and the result of a large di/dt, combined with the on-die inductance and capacitance of the power grid.
Analog droop detectors work by amplifying the droop signal so that the signal has a large enough amplitude to be detectable. The problem with these droop detectors is that, for a droop event of a very short duration (a very narrow droop), such as a 0th droop event, the amplifier must have a very high bandwidth in order to sufficiently amplify the signal for it to be detectable. High-bandwidth amplifiers are very difficult to make. Thus, droop detectors are either very fast, but not very sensitive, or very sensitive, but not very fast. In either case, a 0th droop event will be missed.
Because the 0th droop has not been measure with precision, engineers have been unable to ascertain either the amplitude or the quantitative impact of a 0th droop event on a microprocessor.
Thus, there is a continuing need for a droop detector that overcomes the shortcomings of the prior art.